Many gas turbine engines utilize a small turbine powered by hot pressurized air for starting a main turbine engine. These small turbines, typically known as air turbine starters, commonly have air delivered to them at high air temperatures on the order of 1175.degree. F. For this purpose, the air turbine starters are conventionally adapted to receive compressed air from a ground cart or the like.
As an alternative, an auxiliary or emergency power unit might conveniently be utilized to deliver air to the air turbine starters. Unfortunately, due to the typical low temperature of air from such sources, e.g., on the order of 400.degree. F., much power would be lost. For this reason, the auxiliary power unit would necessarily need to be larger to supply a greater volume of air to compensate for the power loss.
Of course, this is most undesirable in aircraft where weight constraints are known to be of considerable concern. Thus, any increase in the size of the auxiliary or emergency power unit would necessarily result in substantially increased cost, weight and space requirements. In addition, depending upon the approach, it could turn out that a substantially increased pressure loss would be encountered.
The present invention is directed to overcoming the above stated problems by providing a unique combustion heated air turbine starter system.